Quote 1
The impression I had was that we were leaving the West and entering the East. (1.1)
Harker considers Budapest, the capital of Hungary, to be the last outpost of "the West" as he enters "the East." It's a total cultural change after crossing the river—in the "East," everyone is superstitious and caught up in traditions. Also, there are vampires.
Quote 2
This was the being I was helping to transfer to London, where, perhaps, for centuries to come he might, amongst its teeming millions, satiate his lust for blood, and create a new and ever-widening circle of semi-demons to batten on the helpless. The very thought drove me mad. (4.62)
Jonathan imagines Dracula invading England and glutting himself on the blood of English people. He feels powerless to stop him, and imagines that the English will be likewise "helpless" against the vampire.
Quote 3
There was something about them that made me uneasy, some longing and at the same time some deadly fear. I felt in my heart a wicked, burning desire that they would kiss me with those red lips. It is not good to note this down, lest some day it should meet Mina's eyes and cause her pain; but it is the truth. (3.29)
Jonathan's repressed sexual desire comes bubbling to the surface when he sees the sexy vampire ladies in Castle Dracula. He's both attracted to them and repulsed by them, and ashamed to admit that he kind of wants them to kiss him.